15-keto-13-14-dihydroprostaglandin-f2alpha and Bronchial-Hyperreactivity

We studied the effect of intravenous administration of 13,14-dihydro-15-keto-prostaglandin (PG) F2 alpha on airway responsiveness to histamine and airway wall thickening in guinea-pigs. Guinea-pigs were killed and the lungs were fixed in formalin. Slides from paraffin-embedded sections of the lungs were stained and the airways that were cut in transverse section were measured by tracing enlarged images using a digitizer. Moreover, airway resistance (Raw) was determined by a pulmonary mechanics analyser and we calculated two indices, an index of airway wall thickening and the one of airway hyperresponsiveness to histamine, from changes of baseline-Raw and peak-Raw following intravenous administration of histamine before and after the intravenous administration of 13,14-dihydro-15-keto-PGF2 alpha. Intravenous administration of 10 micrograms/kg 13,14-dihydro-15-keto-PGF2 alpha for 1 h did not induce an increase of the relative thickness of the airway wall by the histological examination. In analysis of airway function, intravenous administration of 10 micrograms/kg 13,14-dihydro-15-keto-PGF2 alpha for 1 h induced airway hyperresponsiveness to histamine without airway wall thickening. Thromboxane A2 (TXA2) receptor antagonists ONO-NT-126 and ONO-8809 inhibited the 13,14-dihydro-15-keto-PGF2 alpha-induced airway hyperresponsiveness to histamine, suggesting that the effect of 13,14-dihydro-15-keto-PGF2 alpha on bronchial hyperresponsiveness is likely to be mediated through TXA2.

Topics: Animals; Bridged Bicyclo Compounds; Bronchi; Bronchial Hyperreactivity; Bronchoconstriction; Dinoprost; Fatty Acids, Monounsaturated; Guinea Pigs; Histamine; Infusions, Intravenous; Male; Thromboxane A2

Prostaglandin F2 alpha (PGF2 alpha) has been suggested to play a role in the pathogenesis of bronchial asthma. In this study, the effects of intravenous administration of 13,14-dihydro-15-keto-PGF2 alpha, a stable metabolite of PGF2 alpha, on bronchial smooth muscle in guinea pigs were investigated by measuring dynamic respiratory resistance using a formula that excludes the effects of differences in airway wall thickness. With this formula, the ratio of bronchial smooth muscle constriction by histamine can be estimated as an index of bronchial hyperresponsiveness. Administration of 13,14-dihydro-15-keto-PGF2 alpha did not induce airway wall edema. The ratio of bronchial smooth muscle constriction by histamine was significantly enhanced by the administration of 13,14-dihydro-15-keto-PGF2 alpha. Moreover, TXA2 antagonists, ONO-NT-126 and ONO-8809, inhibited the effect of 13,14-dihydro-15-keto-PGF2 alpha administration. These results suggest that 13,14-dihydro-15-keto-PGF2 alpha can be important mediators affecting bronchial hyperresponsiveness, and TXA2 may play a part in the 13,14-dihydro-15-keto-PGF2 alpha-induced bronchial hyperresponsiveness.

Topics: Administration, Oral; Animals; Bridged Bicyclo Compounds; Bronchi; Bronchial Hyperreactivity; Bronchoconstriction; Dinoprost; Fatty Acids, Monounsaturated; Guinea Pigs; Histamine; Injections, Intravenous; Male; Thromboxane A2